The Hypoglycaemic Effects of the New Zealand Pine Bark Extract on Sucrose Uptake and Glycaemic Responses in Healthy Adults-A Single-Blind, Randomised, Placebo-Controlled, Crossover Trial

Abstract

Background: The New Zealand pine bark has been demonstrated in vitro to inhibit digestive enzymes involved in carbohydrate digestion (alpha-amylase, alpha-glucosidase, and dipeptidyl-peptidase 4 (DPP-4)).

Objective: This study aims to investigate the inhibitory effects of the New Zealand pine bark on sucrose uptake and glycaemic responses in humans.

Methods: A single-blind, randomised, placebo-controlled, crossover trial was carried out involving healthy adults (n = 40 (M: 12, F: 28), 30.1 ± 1.3 years, BMI 23.4 ± 0.5 kg/m², HbA1c 32.5 ± 0.6 mmol/mol, FBG 4.7 ± 0.1 mmol/L). A control (75 g of sucrose powder only), and two doses of the pine bark extract (50 and 400 mg) were provided on separate occasions, with 75 g of sucrose mixed in 250 mL of water. Blood samples were collected at -10, 0, 15, 30, 45, 60, 90, and 120 min via a finger prick test. A linear mixed model for repeated measures (SPSS v30, IBM) was applied, and data presented as model-adjusted mean ± SEM.

Results: Compared to control (247.5 ± 14.0 mmol/L⋅min), the iAUCglucose was significantly reduced with the 400 mg dose (211.8 ± 13.9 mmol/L⋅min, 14.4% reduction, and p = 0.037), but not with 50 mg dose (220.8 ± 14.2 mmol/L⋅min, 10.8% reduction, and p = 0.184). Compared to control (9.1 ± 0.2 mmol/L), glucose peak value was significantly reduced with the 50 mg dose (8.6 ± 0.2 mmol/L, 5.5% reduction, and p = 0.016) but not with the 400 mg dose (8.7 ± 0.2 mmol/L, 4.4% reduction, and p = 0.093). There were no statistically significant changes in postprandial insulin levels with the pine bark extract compared to control.

Conclusions: The New Zealand pine bark extract attenuated sucrose uptake with improved glycaemic responses, and may therefore be useful as a hypoglycaemic adjunct to the diet.

Keywords: bioactives; glucose intolerance; hyperglycaemia; plant extract; postprandial glucose; postprandial insulin; proanthocyanin; sucrose inhibition; type 2 diabetes.

Figure 1

CONSORT diagram for the pine bark Study.

Figure 2

Changes in mean postprandial glucose (mmol/L) (± SEM) from 0 to 120 min of participants (n = 40) in each intervention (50 and 400 mg of pine bark extract compared to control). * Statistically significant differences were detected at 45 min with 400 mg of pine bark extract and 90 min with 50 mg of pine bark extract compared to control (p < 0.05).

Figure 3

Changes in mean postprandial insulin (mU/L) (±SEM) from 0 to 120 min of participants (n = 40) in each intervention (50 and 400 mg of pine bark extract compared to control).